Patterns of vertical distribution and migration of zooplankton at Ocean Station “P” PublicDeposited

Descriptions

Stratified bongo net samples taken at depths between 0 and 500 m at Ocean Station “P” in the subarctic Pacific in early July 1971 have been analyzed to determine the vertical structure of the zooplankton community. Distributions for 99 categories of animals have been grouped by factor analysis into five basic patterns: surface dwellers, a bimodal subsurface pattern, and three patterns of deep-dwelling forms with progressively deeper upper limits. Diurnal vertical migration was restricted to a very small fraction of the species present, primarily those previously described as strong migrators. The upward migration of some of these species stopped in the thermocline between 25 and 100 m. The minimum of biomass density found between 75 and 200 m by earlier workers was confirmed, and a similar minimum was found in the distribution of a number of species.